Sayhi2steve Posted April 22, 2003 Report Share Posted April 22, 2003 :-? Hi All was wondering if anyone knew, If you buy a submersible pump that pumps say 486 gph at 2ft of head does it also mean that if it is submerged 2ft under the water it will pump 486 gph or will it pump the 642 gph that it can pump at 0 ft of head. Hope that made sense and very interested in hearing from anyone who knows. Thanks Steve Quote Link to comment Share on other sites More sharing options...
ajbroome Posted April 22, 2003 Report Share Posted April 22, 2003 Sayhi2steve said... > ... was wondering if anyone knew... I'd *guess* that it'd be somewhere in between the two extremes. Andrew. Quote Link to comment Share on other sites More sharing options...
Midas Posted April 22, 2003 Report Share Posted April 22, 2003 In theory it should pump close to the 0ft rating. The extra suction head provided by imersion in the water can be subtracted from the head provided by the height of water the pump is pushing against. e.g. If a pump is being used to return water from a sump to a tank, the height of water that the pump has to push against is the difference between the water level of the sump and of the tank. Not the distance between where the pump is located to the water level in the tank. Quote Link to comment Share on other sites More sharing options...
Sayhi2steve Posted April 23, 2003 Author Report Share Posted April 23, 2003 Thanks Midas wondered if the pressure of it being underwater made the pump struggle like it was pumping water uphill. In otherwords Head. Quote Link to comment Share on other sites More sharing options...
Ira Posted April 23, 2003 Report Share Posted April 23, 2003 Nah, it wouldn't struggle against the water pressure. The water pressure would be pushing the water from the intake of the pump up through the hose to the waters surface. The only difference between having the pump 2 feet under water and having it at the waters surface would be the extra 2 feet of hose. Which...Wouldn't be any real resistance to the water flow. Quote Link to comment Share on other sites More sharing options...
john1 Posted April 23, 2003 Report Share Posted April 23, 2003 Hi I am not an engeneer. So, I can only talk of "experience" I had. I put a powerhead in the bathtub and tried out the flow. Makes no difference where the pump is. If you submerse it 3 feet under water, wait for the water to equalize, the switch the pump on. It still has to overcome the WEIGHT of the water. So in a nutshell, 2 feet height is 2 feet height. Wherever the pump is. John Quote Link to comment Share on other sites More sharing options...
Interfecus Posted April 24, 2003 Report Share Posted April 24, 2003 The height is measured above water level. While submerged without lifting above the water level it can be considered to be pumping at the 0 ft level. This is because equal pressure is exerted on either end of the pump by the water. If you were pumping above the water level then the water column above the outlet would be higher than the one above the inlet which would slow the pumping by making the pump push against an extra force exerted on the outlet side. Quote Link to comment Share on other sites More sharing options...
john1 Posted April 24, 2003 Report Share Posted April 24, 2003 Hi I originally bought this powerhead to pump a 25l container on the floor into my tank. I have a backproblem. As I said before I tried it in the bathtub first. The pump is rated at 900l/h. AT ZERO height. According to the chart it should still pump 200l/h at 1 meter height. At 1 meter NOTHING comes out. It might if the inlet is 1 meter high and the outlet is 1 meter high. But straight from the floor it is hopeless. If it would take 1/2 hour to pump the 25l into my tank, I would not mind. I have a smoke and a coffee. But it just does not work. One needs a much more powerful pump. Like a bilge pump. So, the cheapest way of doing it, I let my missus do the lifting. Good exercise. John Quote Link to comment Share on other sites More sharing options...
Ira Posted April 24, 2003 Report Share Posted April 24, 2003 If the inlet is 1 meter high and the outlet is 1 meter high then that's 0 head. Quote Link to comment Share on other sites More sharing options...
Warren Posted April 25, 2003 Report Share Posted April 25, 2003 Just to add my 2 cents worth. The head is basically the difference in height between the water surface and the hose outlet. If the outlet is above the water surface you have positive head and if it is below you have negative head. It does not matter how deep the pump is under the water surface as long as it is rated for the depth. The head is measured from the water surface only. An immersed powerhead should pump its rated L/hr if simply immersed. Any pipe or hose connected will lower the flow due to drag in the pipe/hose. The longer and smaller the pipe, the more drag and less flow. So, if the pump is at the bottom of the tank and the connected hose comes out of the tank, drops 1m then rises 1.5m to the filter edge then hangs over the filter edge by 200mm then the head is 300mm. The pump must have some flow at 500mm head or it will never get started. Quote Link to comment Share on other sites More sharing options...
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